Treatment for rubber-reinforcing fibers, reinforcing fibers, and reinforced rubbers

ABSTRACT

A reinforcing fiber for a rubber product that has excellent heat resistance, water resistance and resistance to flex fatigue without undergoing a complicated production process and a treatment agent therefore. This treatment agent comprises a rubber latex, a resorcin-formaldehyde water-soluble condensate and triazine thiol.

CROSS-REFERENCE

This application is a 371 application of PCT/JP97/02350 filed Jul. 7,1997.

TECHNICAL FIELD

The present invention relates to a rubber-reinforcing fiber treatmentagent, a reinforcing fiber and a rubber-reinforced product. Morespecifically, it relates to a treatment agent for a rubber-reinforcingfiber that is used to reinforce rubber products such as a rubber belt,tire and the like and is excellent in adhesion, heat resistance, flexingresistance and water resistance; a rubber-reinforcing fiber coated withthe treatment agent; and a rubber-reinforced product reinforced with thereinforcing fiber.

BACKGROUND ART

As a reinforcement for a rubber product such as a rubber belt, tire andthe like, reinforcing fibers such as glass fibers, polyester fibers,polyamide fibers and the like are widely used.

Since a rubber product such as a rubber belt and the like undergoes flexstress repeatedly, its performance degrades due to its flex fatigue,whereby a reinforcing fiber may be separated from a rubber matrix orworn out, with the result that its strength lowers easily. Such aphenomenon tends to be accelerated by heat and moisture, in particular.To prevent such flex fatigue by separation and obtain a sufficientreinforcing effect, drape and adhesion between a reinforcing fiber andrubber must be increased, and heat resistance and water resistance mustbe provided to the reinforcing fiber. To this end, various treatmentagents are coated on the surface of a reinforcing fiber.

JP-A 1-221433 proposes various treatment agents such as a treatmentagent comprising a resorcin-formaldehyde water-soluble condensate,vinylpyridine-butadiene-styrene terpolymer latex, dicarboxylatedbutadiene-styrene copolymer latex and chlorosulfonated polyethylenelatex in combination.

Although the use of these treatment agents can improve adhesion betweena reinforcing fiber and a rubber matrix and the heat resistance andflexing resistance of a treatment agent itself to a certain degree, itcannot yet be said that they are satisfactory. Therefore, rubberproducts having excellent heat resistance, water resistance andresistance to flex fatigue are difficult to obtain when reinforcingfibers treated with these treatment agents are used.

To increase adhesion between the reinforcing fiber and a rubber matrix,JP-B 5-71710 also proposes a rubber-reinforcing fiber formed bylaminating the second layer containing a halogen-containing polymer andisocyanate on the first layer formed on a reinforcing fiber andcontaining a resorcin-formaldehyde water-soluble condensate and a latexand further laminating the third layer containing the same rubber asmatrix rubber on the second layer. The production process of therubber-reinforcing fiber of this type, however, is complicated anduneconomical since the second and third layer-forming steps arerequired, subsequently to the first layer-forming step.

DISCLOSURE OF INVENTION

It is the first object of the present invention to provide a fibertreatment agent for a reinforcing fiber, which solves the above problemsof the prior art and can give reinforced rubber products havingexcellent heat resistance, water resistance and resistance to flexfatigue without undergoing a complicated production process.

It is the second object of the present invention to provide the abovereinforcing fiber treated with the fiber treatment agent of the presentinvention.

It is the third object of the present invention to provide a reinforcedproduct reinforced with the reinforcing fiber of the present invention.

Other objects and advantages of the present invention will becomeapparent from the following description.

According to the present invention, firstly, the above objects andadvantages of the present invention can be attained by arubber-reinforcing fiber treatment agent comprising a rubber latex, aresorcin-formaldehyde water-soluble condensate and triazine thiol.

According to the present invention, secondly, there is provided areinforcing fiber treated with the above fiber treatment agent of thepresent invention and, thirdly, there is provided a rubber-reinforcedproduct reinforced with the rubber-reinforcing fiber of the presentinvention.

The present invention will be described in detail hereinafter.

(Rubber-reinforcing Fiber Treatment Agent)

As the rubber latex which is one of the components of therubber-reinforcing fiber treatment agent of the present invention may bepreferably used a butadiene-styrene copolymer latex, dicarboxylatedbutadiene-styrene copolymer latex, vinylpyridine-butadiene-styreneterpolymer latex, chloroprene latex, butadiene rubber latex,chlorosulfonated polyethylene latex, acrylonitrile-butadiene copolymerlatex, nitrile group-containing highly saturated copolymer rubber latexand the like. These latices may be used alone or in admixture of two ormore. A favorable result can be obtained in many cases by using a latexof rubber, which is the same as or similar to rubber to be reinforced intype, as the rubber latex to be contained in the rubber-reinforcingfiber treatment agent. A particularly favorable result can be obtainedby applying a fiber treatment agent containing nitrile group-containinghighly saturated copolymer rubber latex to a fiber for reinforcing arubber blend that contains nitrile group-containing highly saturatedcopolymer rubber.

As the butadiene-styrene copolymer rubber latex, it is particularlysuitable to use, for example, a copolymer prepared by copolymerizingbutadiene and styrene in a weight ratio of 60:40 to 90:10. Preferredexamples of this latex include JSR 2108 (trade name, manufactured byJapan Synthetic Rubber Co., Ltd.), Baystal S60 (trade name, manufacturedby Bayer AG), J9040 (trade name, manufactured by Sumika ABS Latex Co.,Ltd.), Nipol LX110 (trade name, manufactured by Nippon Zeon Co., Ltd.)and the like.

As the dicarboxylated butadiene-styrene copolymer latex, a copolymercomprising 20 to 80 wt % of butadiene, 5 to 70 wt % of styrene and 1 to10 wt % of an ethylenic unsaturated dicarboxylic acid is particularlysuitable, for example. Preferred examples of this latex include Nipol2570X5 (trade name, manufactured by Nippon Zeon Co., Ltd.), JSR 0668(trade name, manufactured by Japan Synthetic Rubber Co., Ltd.) and thelike.

As the vinylpyridine-butadiene-styrene terpolymer latex may be used, forexample, many terpolymers of this type known to those skilled in theart. For example, a terpolymer comprising vinylpyridine, butadiene andstyrene in a weight ratio of 10:80:10 to 20:60:20 is particularlysuitable. Preferred examples of this terpolymer include Nipol 2518FS(trade name, manufactured by Nippon Zeon Co., Ltd.), JSR 0650 (tradename, manufactured by Japan Synthetic Rubber Co., Ltd.), Pyratex (tradename, manufactured by Sumika ABS Latex Co., Ltd.) and the like.

As the chlorosulfonated polyethylene latex, a polymer having a chlorinecontent of 25 to 43 wt % and a sulfur content of 1.0 to 1.5 wt % isparticularly suitable. Preferred examples of this terpolymer includeCSM-450 (trade name, manufactured by Sumitomo Seika Chemicals Co., Ltd.)and the like.

As the acrylonitrile-butadiene copolymer latex, a copolymer containing30 to 43% of bound acrylonitrile is particularly suitable. Preferredexamples of this latex include Nipol 1561 (trade name, manufactured byNippon Zeon Co., Ltd.) and the like.

The nitrile group-containing highly saturated polymer rubber latexpreferably has an iodine valence of 120 or less from the viewpoint ofthe strength of a rubber film and the adhesion strength to matrixrubber. The valence of iodine is preferably 0 to 100. The content(amount of bound acrylonitrile) of unsaturated nitrile units in thenitrile group-containing highly saturated polymer rubber is preferably10 to 60 wt % from the viewpoint of adhesion and drape for the matrixrubber. Illustrative examples of the nitrile group-containing highlysaturated polymer rubber include hydrogenated products ofbutadiene-acrylonitrile copolymer rubber,isoprene-butadiene-acrylonitrile copolymer rubber andisoprene-acrylonitrile copolymer rubber; butadiene-methylacrylate-acrylonitrile copolymer rubber, butadiene-acrylicacid-acrylonitrile copolymer rubber and hydrogenated products thereof;butadiene-ethylene-acrylonitrile copolymer rubber, butylacrylate-ethoxyethyl acrylate-vinyl chloroacetate-acrylonitrilecopolymer rubber, butyl acrylate-ethoxyethylacrylate-vinylnorbornene-acrylonitrile copolymer rubber and the like. Asthe latex may be preferably used “Zetpol Latex” (trade name,manufactured by Nippon Zeon Co., Ltd.). The valence of iodine isdetermined in accordance with JIS K 0070.

The resorcin-formaldehyde water-soluble condensate (to be abbreviated asRF hereinafter) which is the second component of the rubber-reinforcingfiber treatment agent of the present invention is preferably, forexample, a resol-type water-soluble addition condensate obtained byreacting resorcin with formaldehyde in the presence of an alkalinecatalyst such as alkali hydroxide or amine, particularly preferably areaction product obtained by reacting resorcin with formaldehyde in amolar ratio of 1:0.5 to 3.

Illustrative examples of the triazine thiol, which is the mostcharacteristic component of the rubber-reinforcing fiber treatment agentof the present invention, include 1,3,5-triazine-2,4,6-trithiol,6-amino-1,3,5-triazine-2,4-dithiol,6-dibutylamino-1,3,5-triazine-2,4-dithiol and the like. Of these,1,3,5-triazine-2,4,6-trithiol is preferred. It is preferred thattriazine thiol is ground to a particle size of 0.1 to 1.0 μm by a ballmill or the like, and dispersed into a dispersant such as water to aconcentration of, for example, 10 to 50 wt % before use. The dispersantused is not particularly limited, and other dispersants such as alcoholsmay be used, in addition to water.

As an oxidizing agent may be used an organic peroxide, chloranil,benzoquinone, resorcinol and the like. Of these, chloranil isparticularly preferred.

In the present invention, the proportions of the rubber latex, RF,triazine thiol and oxidizing agent are preferably 50 to 95 wt % (morepreferably 65 to 85 wt %), 2 to 25 wt % (more preferably 5 to 20 wt %),0.5 to 20 wt % (more preferably 2 to 10 wt %) and 0 to 10 wt % (morepreferably 0 to 5 wt %) in terms of the ratio of solid contents,respectively. Water is added to these as required, and the resultingmixture is uniformly mixed to prepare an aqueous treatment solution.When the solid content ratio of the triazine thiol contained in the thusobtained rubber-reinforcing fiber treatment agent of the presentinvention is outside the above range, the improvements of heatresistance, water resistance and resistance to flex fatigue are notobserved and the effect of the present invention is not obtainedsufficiently. Although the effect of the present invention is stillobtained even if the oxidizing agent is not added, heat resistance,water resistance and resistance to flex fatigue are further improvedwhen it is added. In this case, when the proportion of the oxidizingagent exceeds the above range, the effect remains unchanged. When theproportion of the RF is too large, the coating film of the treatmentagent of the present invention becomes hard, whereby a reinforcing fiberbecomes hard and sufficient resistance to flex fatigue is hardlyobtained. When the proportion of the RF is too small, sufficientadhesion to a rubber matrix is hardly obtained.

The solid content of the aqueous treatment agent of the presentinvention is 10 to 40 wt %, preferably 20 to 30 wt %. When the solidcontent is too small, build-up on a reinforcing fiber becomesinsufficient, while when the solid content is too large, it is difficultto control the amount of build-up on the reinforcing fiber, therebymaking it difficult to obtain a rubber-reinforcing fiber having theuniform amount of build-up.

Although the treatment agent of the present invention comprises theabove rubber latex, RF and triazine thiol as essential ingredients, itmay also contain a base such as ammonia to control its pH and furthercontain sulfur, stabilizer, antioxidant and the like as required, inaddition to the above oxidizing agent.

(Rubber-reinforcing Fiber)

A fiber for the rubber-reinforcing fiber usable in the present inventionis not particularly limited. Specific examples of the fiber includeglass fiber; polyvinyl alcohol fibers typified by vinylon fiber;polyester fibers; polyamide fibers such as nylon and aramid (aromaticpolyamide); carbon fibers; polyparaphenylene benzoxazole fibers; and thelike. Of these, glass fiber and aramid fiber are particularly preferred.These fibers may be in various forms, and specific examples of suchforms include staple, filament, cord, rope, canvas or the like. Theglass composition of the glass fiber is not limited, as exemplified byE-glass, high-strength glass and the like. The filament diameter of theglass fiber is also not particularly limited but is generally 5 to 13μm. The aramid fiber of 500 to 5,000 denier is generally used.

(Treatment of rubber-reinforcing Fiber)

The method for treating the above fiber is not particularly limited inthe present invention. Before the fiber is treated with the treatmentagent of the present invention, it can be suitably treated with anepoxy, polyisocyanate or silane coupling agent according to the type ofthe fiber. One example of the method is as follows.

A glass fiber strand as the fiber is immersed in the treatment agent ofthe present invention and pulled up to remove a surplus of the treatmentagent, and the strand is heated at 200 to 300° C. for 0.5 to 3 minutesas required to build up the treatment agent on the surface of the glassfiber strand. On this occasion, the glass fiber strand may or may not betreated with greige goods at the time of spinning. A desired number ofthe glass fiber strands are bundled and twisted in an ordinary way toobtain a rubber-reinforcing fiber (cord). This rubber-reinforcing fiberis buried into an unvulcanized rubber matrix by a known method per se,and the unvulcanized rubber matrix is vulcanized by heating at 120 to180° C. under pressure for 1 to 120 minutes.

In the above method, the treatment agent of the present invention iscoated on the fiber generally in an amount of 10 to 30 wt % as a solidcontent, based on the weight of the fiber treated with the fibertreatment agent. The type of rubber to be reinforced with arubber-reinforcing fiber treated with the treatment agent of the presentinvention is not particularly limited, and there may be used varioustypes of rubber such as chloroprene rubber, chlorosulfonatedpolyethylene rubber, nitrile group-containing highly saturated copolymerrubber and the like. Particularly when nitrile group-containing highlysaturated copolymer rubber is used, an extremely favorable result can beobtained. When a rubber-reinforcing fiber cord coated with the treatmentagent of the present invention is buried into the rubber which is to bevulcanized, additives to be generally added to rubber, such as avulcanizer, vulcanizing accelerator, pigment, fats and oils, andstabilizer may be added according to purpose. The content of therubber-reinforcing fiber cord in a rubber product obtained aftervulcanization and molding, though determined depending on the type ofthe rubber product, is generally 10 to 70 wt %, preferably 20 to 40 wt%.

A rubber product obtained by the present invention is excellent in heatresistance, water resistance and resistance to flex fatigue. Therefore,a rubber-reinforcing fiber treated with the fiber treatment agent of thepresent invention can be advantageously used as a reinforcing fiber fora rubber-reinforced product such as an auto timing belt which undergoesflex stress in an environment influenced by heat and moisture.

The following examples are given to further illustrate the presentinvention. In the following examples, “parts” and “%” are based onweight unless otherwise stated.

EXAMPLES

(Preparation of Rubber Blend)

A rubber blend was prepared according to the formulation shown inTable 1. In the table, “Zetpol 2020” is nitrile group-containing highlysaturated copolymer rubber (trade name, manufactured by Nippon Zeon Co.,Ltd.) having an iodine valence of 28 and comprising 36% of boundacrylonitrile.

TABLE 1 formulation parts Zetpol 2020 100.0 zinc white No. 1 5.0 stearicacid 1.0 trioctyl trimellitate 10.0 SRF carbon 60.04,4-(α,α-dimethylbenzyl) diphenylamine 1.5 mercaptobenzothiazole zincsalt 1.5 tetramethylthiuram disulfide 1.5 sulfur 0.5cyclohexylbenzothiazyl sulfenamide 1.0

(Preparation of RF Solution)

An RF solution was prepared in accordance with the formulation shown inTable 2.

TABLE 2 resorcin 7.8 parts formalin (37%) 6.9 parts aqueous solution ofsodium hydroxide (10%) 2.0 parts water 115.2 parts

(Preparation of Treatment Agent)

Seven treatment agents A to G were prepared using the RF solution shownin Table 2 in accordance with the formulation shown in Table 3 (the unitof figures below each treatment agent is “parts”). In the table, “Nipol2518FS” is a vinylpyridine-butadiene-styrene terpolymer latex (productof Nippon Zeon Co., Ltd.; a solid content of 40%), “CSM-450” is achlorosulfonated polyethylene rubber latex (product of Sumitomo SeikaChemicals Co., Ltd.; a solid content of 40%), and “Zetpol Latex” isnitrile group-containing highly saturated copolymer rubber latex(product of Nippon Zeon Co., Ltd.; an iodine valence of 28, 36% of boundacrylonitrile and a solid content of 40%). The solid content of eachtreatment agent was 25 to 27 wt %.

TABLE 3 treatment agent A B C D E F G RF solution 35.0 35.0 35.0 30.035.0 35.0 30.0 Nipol 2518FS — — 10.0 45.0 — 10.0 45.0 CSM-450 — — — 20.0— — 20.0 Zetpol Latex 60.0 60.0 50.0 — 60.0 50.0 — 1,3,5-triazine-2,4,6-3.0 3.0 2.0 1.5 — — — trithiol chloranil 1.0 — 1.0 0.8 — — — 25% ammoniawater 1.0 1.0 1.0 1.0 1.0 1.0 1.0 water 4.0 4.0 4.0 4.0 4.0 4.0 4.0

(Production of Treated Fiber)

This treatment agent was coated on a glass fiber strand (filamentdiameter of 9 μm, 101 tex (600 filaments)) having non-alkali glasscomposition (64.4 wt % of SiO_(2,) 25.0 wt % of Al₂O₃, 0.3 wt % of CaO,10.0 wt % of MgO, 0.1 wt % of B₂O₃ and 0.2 wt % of Na₂O+K₂O) to ensurethat the build-up rate of a solid content is to be about 19%. After thecoated glass fiber strand was heated at 280° C. for 1 minute, it wasfirst twisted 2.1 times per inch in one direction. Thereafter, 11 ofsuch strands were combined together and twisted 2.1 times per 1 inch inthe opposite direction to give a glass fiber cord.

Similarly, the above treatment agent was coated on an aramid fiberstrand (Technora T202 of Teijin Ltd., 1,500 d) to ensure that thebuild-up rate of a solid content is to be about 12%. After the coatedaramid strand was heated at 250° C. for 1 minute, two of such strandswere combined together and twisted 3.1 times per 1 inch to give anaramid fiber cord.

(Evaluation method)

The thus obtained treated cords were arranged to a length of 12 cm and awidth of 25 mm on a sheet of the above rubber blend and vulcanized at atemperature of 150° C. and a pressure of 5 MPa for 30 minutes to give anadhesion strength test piece. A peel test was conducted on the obtainedtest piece to measure initial adhesion. The content of the above treatedcord in the test piece was 30 wt %.

A test piece obtained similarly was heated in an air oven at 120° C. for168 hours, and a peel test was conducted on the test piece to measureits heat-resistant adhesion. A test piece obtained similarly was boiledin water for 1 hour to measure its adhesion (water resistant adhesion).The results are classified by the rubber latex components of the fibertreatment agents and shown in Tables 4 to 7.

Further, a toothed belt having a width of 19 mm and a length of 980 mmwas prepared using a treated fiber cord obtained similarly and thenitrile group-containing highly saturated copolymer rubber blend shownin Table 1. This toothed belt was set in a traveling tester equippedwith a 6,000-rpm drive motor, and a heat-resistant traveling test wasconducted at 120° C. for 600 hours. Another toothed belt obtainedsimilarly was set in a water-injection traveling tester equipped with a6,000-rpm drive motor, and a water-injection traveling test was alsoconducted at room temperature for 24 hours. The tensile strength of thebelt after the heat-resistant traveling test and that after thewater-injection traveling test were measured, respectively, and theratio of each tensile strength to the tensile strength before thecorresponding traveling test, that is, tensile strength retention (%)was obtained. The results are shown in Tables 4 to 7 as tensile strengthretentions after heat-resistant traveling and water-injection traveling.

TABLE 4 Example Comparative 1 2 Example 1 type of cord glass fiber cordglass fiber cord treatment agent No. A B E adhesion (kg/25 mm) initial28.6 26.9 21.5 heat resistant 25.5 23.3 17.8 water resistant 28.3 27.420.5 tensile strength retention after traveling test (%) heat-resistanttraveling 86.4 80.5 72.5 water-injection traveling 76.0 74.7 65.8

TABLE 4 Example Comparative 1 2 Example 1 type of cord glass fiber cordglass fiber cord treatment agent No. A B E adhesion (kg/25 mm) initial28.6 26.9 21.5 heat resistant 25.5 23.3 17.8 water resistant 28.3 27.420.5 tensile strength retention after traveling test (%) heat-resistanttraveling 86.4 80.5 72.5 water-injection traveling 76.0 74.7 65.8

TABLE 6 Comparative Example 4 Example 3 type of cord glass fiber cordglass fiber cord treatment agent No. D G adhesion (kg/25 mm) initial26.5 19.5 heat resistant 20.7 15.6 water resistant 20.2 13.7 tensilestrength retention after traveling test (%) heat-resistant traveling73.3 58.7 water-injection traveling 66.5 41.3

TABLE 6 Comparative Example 4 Example 3 type of cord glass fiber cordglass fiber cord treatment agent No. D G adhesion (kg/25 mm) initial26.5 19.5 heat resistant 20.7 15.6 water resistant 20.2 13.7 tensilestrength retention after traveling test (%) heat-resistant traveling73.3 58.7 water-injection traveling 66.5 41.3

A rubber product reinforced with the rubber-reinforcing fiber of thepresent invention is inexpensive and has excellent heat resistance,water resistance and resistance to flex fatigue, as compared with aconventional treatment agent. The rubber-reinforcing fiber of thepresent invention can be extremely advantageously used as a reinforcingfiber for a rubber-reinforced product such as a belt exemplified by atoothed belt, V belt and the like.

What is claimed is:
 1. A rubber-reinforcing fiber treatment agentcomprising a nitrile group-containing highly saturated copolymer rubberlatex, a resorcin-formaldehyde water-soluble condensate and triazinethiol.
 2. The rubber-reinforcing fiber treatment agent of claim 1, whichcomprises a nitrile group-containing highly saturated copolymer rubberlatex, a resorcin-formaldehyde water-soluble condensate, triazine thioland an oxidizing agent.
 3. The rubber-reinforcing fiber treatment agentof claim 1 or 2, which contains 50 to 95 wt % of the nitrilegroup-containing highly saturated copolymer rubber latex, 2 to 25 wt %of the resorcin-formaldehyde water-soluble condensate, 0.5 to 20 wt % oftriazine thiol and 0 to 10 wt % of the oxidizing agent as solidcontents, based on the total weight of all the solid contents.
 4. Therubber-reinforcing fiber treatment agent of claim 1 or 2, wherein thetriazine thiol is 1,3,5-triazine-2,4,6-trithiol.
 5. Therubber-reinforcing fiber treatment agent of claim 2, wherein theoxidizing agent is chloranil.
 6. The rubber-reinforcing fiber treatmentagent of claim 3, which contains a nitrile group-containing highlysaturated copolymer rubber latex, a resorcin-formaldehyde water-solublecondensate, triazine thiol and an oxidizing agent in the total solidcontent of 10 to 40 wt %.
 7. A rubber-reinforcing fiber treated with thefiber treatment agent of claim 1 or
 2. 8. The rubber-reinforcing fiberof claim 7, wherein the fiber treatment agent is coated on a fiber in anamount of 10 to 30 wt % as a solid content based on the weight of thefiber treated with the fiber treatment agent.
 9. The rubber-reinforcingfiber of claim 8, wherein the fiber is a glass fiber or an aramid fiber.10. A rubber-reinforced product reinforced with the rubber-reinforcingfiber of claim
 7. 11. A rubber-reinforced product reinforced with therubber-reinforcing fiber of claim 7, wherein a matrix of therubber-reinforced product contains a nitrile group-containing highlysaturated copolymer rubber.
 12. The rubber-reinforced product of claim10, wherein the rubber-reinforcing fiber is contained in an amount of 10to 70 wt %, based on the rubber-reinforced product.
 13. Arubber-reinforced product reinforced with the rubber-reinforcing fiberof claim 8, wherein a matrix of the rubber-reinforced product contains anitrile group-containing highly saturated copolymer rubber.
 14. Arubber-reinforced product reinforced with the rubber-reinforcing fiberof claim 9, wherein a matrix of the rubber-reinforced product contains anitrile group-containing highly saturated copolymer rubber.
 15. Therubber-reinforcing fiber treatment agent of claim 3, wherein thetriazine thiol is 1,3,5-triazine-2,4,6-trithiol.
 16. Therubber-reinforcing fiber treatment agent of claim 3, wherein theoxidizing agent is chloranil.
 17. A rubber-reinforcing fiber treatedwith the fiber treatment agent of claim
 3. 18. A rubber-reinforcingfiber treated with the fiber treatment agent of claim
 4. 19. Arubber-reinforcing fiber treated with the fiber treatment agent of claim5.
 20. A rubber-reinforcing fiber treated with the fiber treatment agentof claim
 6. 21. A rubber-reinforced product reinforced with therubber-reinforcing fiber of claim
 17. 22. A rubber-reinforced productreinforced with the rubber-reinforcing fiber of claim
 18. 23. Arubber-reinforced product reinforced with the rubber-reinforcing fiberof claim
 19. 24. A rubber-reinforced product reinforced with therubber-reinforcing fiber of claim
 20. 25. The rubber-reinforced productof claim 11, which a rubber-reinforcing fiber is contained in an amountof 10 to 70 wt %, based on the rubber-reinforced product.